This section provides background information related to the present disclosure and is not necessarily prior art.
Dynamometers, often referred to simply as “dynos,” are devices that measure the performance of a machine. Most commonly, dynamometers are utilized to measure the performance of a vehicle, and more specifically, the power and torque generated by the vehicle's engine, which is typically transferred to the dynamometer through associated powertrain components. In addition to measuring power and torque, dynamometers can be used to determine friction and pumping losses or to simulate road loading conditions for emissions testing, durability testing, and extreme temperature testing.
There are several forms of dynamometers that are commonly used for vehicle testing. These include engine dynamometers, chassis dynamometers, and powertrain dynamometers. Engine dynamometers couple directly to the vehicle's engine and measure power and torque directly from the engine's crankshaft. Such engine dynamometers typically require the vehicle's engine to be removed from the vehicle and do not account for power losses in the vehicle's drivetrain, gearbox, transmission, or differential. Accordingly, engine dynamometers are typically used by engine manufacturers to test engines before they are installed in a vehicle. Chassis dynamometers generally include a chassis dynamometer roll that is driven by the drive wheels of the vehicle during testing. Chassis dynamometers measure the power delivered to the chassis dynamometer roll by the drive wheels of the vehicle. As such, chassis dynamometers are sometimes referred to as “rolling road” dynamometers because the rotating chassis dynamometer roll simulates on-road operation. Advantageously, chassis dynamometers can be quickly and easily set up and they account for the friction losses associated with the vehicle's drivetrain, thereby providing better approximations of on-road performance.
Before testing, the vehicle can simply be driven up onto the chassis dynamometer rolls and anchored in place. Thus, there is no need to remove the engine from the vehicle for testing. However, some disadvantages of chassis dynamometers include tire wear, which can occur during longer endurance and durability tests, and wheel slip, which can occur between the wheel and the chassis dynamometer roll, resulting in less accurate measurements.
Powertrain dynamometers generally include a powertrain dynamometer shaft that is driven by at least one powertrain component of the vehicle during testing. Typically, the powertrain dynamometer shaft is connected to the hubs of the vehicle for direct power and torque measurement from the vehicle's drive axle. Although the vehicle must be raised on jacks and have its wheels removed before the powertrain dynamometer can be connected, there is no potential for tire wear or wheel slip with this type of dynamometer. In some instances the powertrain dynamometer has special bearings that can support the full weight of the vehicle which allows the vehicle suspension to attain the same position that it would on the road.
All of these various types of dynamometers have some form of dynamometer motor. The dynamometer motor includes a motor shaft that is rotatably coupled to the driven component(s) of the dynamometer. Such dynamometer motors provide power and torque measurements and are typically large components that increase in size as their maximum load range increases. Accordingly, the dynamometer motors used to test heavy duty and multi-axle vehicles take up significant space. Although portable dynamometers exist, many dynamometers are situated inside a test chamber. This is particularly true where vehicle testing requires runs at specific temperatures. For example, many modern day tests require vehicle testing at extreme temperatures including very low temperatures such as −65° C. (Celsius). Test chambers are thus defined by at least one chamber wall that isolates the vehicle from ambient temperatures. Climate control equipment controls the temperature within the test chamber such that the vehicle can be tested at extreme temperatures. Such test chambers are typically large in size because they must provide enough room for not only the vehicle, but also the entire dynamometer assembly, including the dynamometer motor. Also, many test chambers are constructed such that separate chassis dynamometers and powertrain dynamometers can be arranged within the test chamber. This allows use of either type of dynamometer depending on the specific criteria of a particular test without having to move equipment into and out of the test chamber.
The size of such test chambers thus becomes problematic from a climate control standpoint. It becomes very costly to maintain the test chamber at extreme temperatures during a test given the large volume of air within the test chamber that must be heated or cooled. Stated another way, large amounts of energy are consumed in order to maintain large test chambers at extreme temperatures during testing.